The primary aim of this study is to determine if infertile women exposed to ovulation-inducing agents (OIAs) are at increased risk for ovarian cancer as compared to infertile women not exposed to OIAs. The cohort consists of 74,640 women seen for infertility services by one of 15 infertility clinics in California between 1965 and 1995. Tracing and linkage information will be abstracted from computerized listings or medical records for all women comprising the study cohort to verify state of residence. Linkage with state and local tumor registries will be done to identify incident cases of ovarian cancer. Assuming a relative risk of 3, they expect to obtain 267 cases of ovarian cancer. An age-stratified random sample of 2,670 cohort members will serve as the subcohort. Full medical record review and telephone interviews will be conducted for ovarian cancer cases and all subcohort members to gather complete information on OIA exposure as well as reproductive history, health status, and infertility treatment-related conditions. The relationship between OIAs and ovarian cancer will be analyzed using the proportional hazards regression model, adjusted for the case-cohort design. Analyses will consider differences in risk according to formulation, dose, and duration of OIAs as well as among subgroups defined by infertility etiology, parity, anovulation, and demographic characteristics. A second aim of this study is to determine if there is a difference in ovarian cancer risk between infertile women treated with OIAs, presumed fertile women treated with OIAs for timed conception (e.g., because of male-factor infertility or for donor insemination), and fertile women treated with OIAs for the purposes of ovum donation to determine the possible independent effects of infertility and OIAs on ovarian cancer risk. The groups will be comprised of infertile women exposed to OIAs from the above cohort, presumed fertile women exposed to OIAs from participating infertility centers, and 767 ovum donors. Data on ovarian cancer incidence and OIA exposure will be collected and analyzed in the same manner described above. The third aim of this study is to use the same methods to determine if there is a difference in risk for breast and uterine corpus cancers between infertile women exposed to OIAs, infertile women not exposed to OIAs, and fertile women exposed to OIAs.